RFR: 8378110: Add -XX: prefix to settings-file flags in RuntimeMXBean.getInputArguments()

[Oli Gillespie]

On Wed, 18 Feb 2026 15:58:57 GMT, Alan Bateman <alanb at openjdk.org> wrote:

>> Flags passed via a settings file (`.hotspotrc`, or `-XX:Flags=my-file`) do not have the `-XX:` prefix like they would have if passed as command-line args. `JVM_GetVmArguments` then prints these flags also without the prefix, along with command-line flags that _are_ prefixed.
>> 
>> However, users of `JVM_GetVmArguments` expect the arguments to be in a format that they can pass as command-line args, for example [in CDS static_dump](https://github.com/openjdk/jdk/blob/63f00fff921ed4ac0f595a0a013d399700433a2c/src/java.base/share/classes/jdk/internal/misc/CDS.java#L329-L338) - CDS static_dump currently *does not work* if the main VM uses flags from a settings file.
>> 
>> So, always add the `-XX:` prefix to flags from settings files in `JVM_GetVmArguments`. Updated existing test to cover this behaviour.
>> 
>> I looked for existing users of `JVM_GetVmArguments` and they either seem like they'll benefit from this change (CDS, JMH via `RuntimeMXBean.getInputArguments()`) or they won't care.
>> 
>> **Testing**
>> 
>> * Updated the existing InputArgument test with a case that verifies the new behaviour.
>> * Confirmed that CDS static_dump and JMH now work on a VM with flags from a file.
>
> test/jdk/java/lang/management/RuntimeMXBean/InputArgument.java line 70:
> 
>> 68:  * @summary RuntimeMXBean.getInputArguments() handling of flags from settings file.
>> 69:  *
>> 70:  * @author  Oli Gillespie
> 
> We try to avoid introducing new `@author` tags if possible. The git log and git blame is good enough for seeing who contributed code to a file.

Thanks, I just added it for consistency with the others in this file. What's the preference, just remove that line?

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PR Review Comment: https://git.openjdk.org/jdk/pull/29793#discussion_r2823126817